The downside to your idea John, and its has been mentioned before, if you have loads of specialist branches the form will die.
When I set my mind on a car I always join a user forum for the car I have or going to get so I’m a member still to this day for the VW Golf, Seat Leon and currently I’m a member of the KIA users forum.
Just to make my point about the forum dying and with my posting on a KIA user site is, I have a Carens that’s not an ever-so popular model and since I joined last October that section of the forum has had a handful of threads and looks dead. Other part of the same forum are lively because of more popular models but this is for all users so just imagine what it would be like if it were just disabled folk.